This by far is the most dangerous and feared U.S weapon:

The Field Radio.
This was the weapon that Germans and Japanese hated. It was what they feared. It is this which brought upon them the seething wrath of artillery and airstrikes from the heavens.
To illustrate my point, there’s an old World War II saying that goes like this:
If you encounter a unit that you cannot identify, shoot once over their heads so it won’t hit anyone.
- If the response is rapid, precise rifle fire, they’re British.
- If the response is a shitstorm of machine-gun fire, they’re German.
- If they throw down their guns and surrender, they’re either French or Italian.
- If you hear a whistle, and then all of a sudden your position is charged by hundreds of soldiers screaming ‘UUUURRRRRAAAAAA!!!!!’, then they’re Russian. –(Credit for this one goes to Axel Homleid)
- And, if nothing happens for five minutes and then your position is obliterated by artillery or an airstrike…
They’re American.
Field radios allowed the Allies to quickly and easily utilize their massive plethora of ammunition and aircraft to effectively take out Axis forces, whether they be large regiments of many men, or just a single enemy sniper.